Re: [RFC/PATCH 3/4] genirq: system set irq affinities

Max Krasnyanskiy
2008-02-28T00:10:46Z

Besides the notifier stuff it's identical to my genirq patch that I sent to
Thomas and you for the review ~5 days ago.
There are a couple of things you missed.
Current call site for select_smp_affinity() inside request_irq() is incorrect.
It ends up moving irq each time requires_irq() is called, and it is called
multiple times for the shared irqs. My patch moves it into setup_irq() under
if(!shared) check.

Also the following part is unsafe

> +#ifdef CONFIG_CPUSETS
> +static int system_irq_notifier(struct notifier_block *nb,
> + unsigned long action, void *cpus)
> +{
> + cpumask_t *new_system_map = (cpumask_t *)cpus;
> + int i;
> +
> + for (i = 0; i < NR_IRQS; i++) {
> + struct irq_desc *desc = &irq_desc[i];
> +
> + if (desc->chip == &no_irq_chip || !irq_can_set_affinity(i))
> + continue;
> +
> + if (cpus_match_system(desc->affinity)) {
> + cpumask_t online_system;
> +
> + cpus_and(online_system, new_system_map, cpu_online_map);
> +
> + set_balance_irq_affinity(i, online_system);
> +
> + desc->affinity = online_system;
> + desc->chip->set_affinity(i, online_system);
Two lines above should be
irq_set_affinity(i, online_system);

If you look at how irq_set_affinity() is implemented, you'll see this

#ifdef CONFIG_GENERIC_PENDING_IRQ
set_pending_irq(irq, cpumask);
#else
desc->affinity = cpumask;
desc->chip->set_affinity(irq, cpumask);
#endif

set_pending_irq() is the safe way to move pending irqs.

btw It should be ok to call chip->set_affinity() directly from
select_smp_affinity() because in my patch is is guarantied to be called only
for the first handler registration.

Max